1. Field of the Invention
This invention pertains to dual control sustained release drug delivery systems. The novel drug delivery systems contain a core comprising a medicament and a waxy material and a coating layer over the core comprising a pH-independent water-insoluble polymer and a water-soluble polymer. Therapeutically effective amounts of the drug delivery systems may be utilized in a wide variety of pharmaceutically acceptable carriers to prepare medicated sustained release compositions. This invention also relates to methods for preparing these drug delivery systems and the medicated sustained release compositions in which they may be used.
2. Description of the Background
Sustained release compositions for the sequential or timed release of medicaments are well known in the art. Generally such compositions contain medicament particles, normally administered in divided doses two or more times daily, mixed with or covered by a coating material which is resistant to degradation or disintegration in the stomach and/or in the intestine for a selected period of time. Release of the medicament may occur by leaching, erosion, rupture, diffusion or similar actions, depending upon the nature and thickness of the coating material.
A frequently encountered problem in the field of sustained release compositions is that many water-miscible drugs have a tendency to be dumped or surged into the body during the first hour or two after an oral dosage form is ingested. This problem is particularly acute when the sustained release compositions are administered with food.
U.S. Pat. No. 4,789,549, issued to Khan et al. and assigned to Warner-Lambert Company, discloses a sustained release composition comprising a medicament in a water-soluble polymer matrix coated with a semi-permeable membrane coating layer consisting of hydroxypropyl cellulose and cellulose acetate phthalate with polyoxypropylene polyoxyethylene block copolymer and acetylated monoglycerides. The water-soluble polymer matrix is preferably hydroxypropyl methylcellulose.
U.S. Pat. No. 4,816,264, issued to Phillips et al. and assigned to Warner-Lambert Company, discloses a sustained release drug delivery system containing a core comprising a medicament and a cellulosic gelling polymer such as hydroxyethyl cellulose coated with a semi-permeable membrane coating layer comprising a water-soluble cellulosic polymer such as hydroxypropyl cellulose and a water-insoluble acrylic polymer such as Eudragit E30D.
U.S. Pat. No. 4,851,233, issued to Khan et al. and assigned to Warner-Lambert Company, discloses a compressed table binder system consisting essentially of procainamide hydrochloride or sodium meclofenamate, type "H" hydroxyethyl cellulose, and microcrystalline cellulose coated with hydroxyethyl cellulose.
While the above sustained release compositions provide some degree of improved sustained release activity, none of the above compositions are entirely satisfactory. All of the above sustained release compositions have a tendency to rapidly release water-miscible drugs into the body when the sustained release compositions are administered with food. Thus it would be advantageous to prepare a sustained release composition having release properties which are unaffected by the consumption of food. The present invention provides such improved sustained release drug delivery systems without the disadvantages characteristic of previously known products. The present invention also provides methods for preparing these improved sustained release drug delivery systems and the medicated sustained release compositions in which they may be employed.